In previous versions of OSX, the Spotlight (system-wide-search) feature would produce a list of results in a drop-down listing from the top right corner of the screen.
With Yosemite, Spotlight brings up a relatively small window in the middle of the screen. The window can’t be sized or moved. So, it covers up whatever you were working on, and the preview of results can’t be seen properly. Click the image below to enlarge.
On a display of 1920 x 1200 pixels, the Spotlight search results window is about 680×430 pixels in size. So, it’s not quite large enough to fully see the results if an image or document preview is showing.
The window doesn’t have the standard interface buttons for close, maximize, or minimize.
It’s not right for Apple to insist that others strictly adhere to specific user interface guidelines and elements, yet Apple doesn’t offer them in their own programs and features.